Leetcode 1157. Online Majority Element In Subarray

Preprocess an array to support up to 10^4 queries that ask whether any value appears at least threshold times in a subarray arr[left..right] (returning that value or -1). Key constraint: 2*threshold > right-left+1 (so the target is a strict majority), so the challenge is to enable fast per-query majority detection via compact preprocessing of element positions/frequencies.